Actuators and microlithography projection exposure systems and methods using the same

ABSTRACT

An actuator includes a housing, a movable part, and an advancing unit that is at least temporarily connected to the movable part. The advancing unit includes a deformation unit and a deformer configured to deform the deformation unit with a vector component perpendicular to an effective direction of the actuator so that a total length of the deformation unit changes in the effective direction of the actuator as a result of the deformation. The movable part is configured to move in the effective direction of the actuator upon a removal of the vector component on the deformation unit and the deformation unit is disposed along the effective direction of the actuator upon the removal of the vector component on the deformation unit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of, and claims priority under 35 USC120 to, U.S. application Ser. No. 13/009,438, filed Jan. 19, 2011, whichis a continuation of, and claims priority under 35 USC 120 to,international application PCT/EP2009/004892, filed Jul. 7, 2009, whichclaims benefit of German Application No. 10 2008 034 285.8, filed Jul.22, 2008. U.S. application Ser. No. 13/009,438 and internationalapplication PCT/EP2009/004892 are hereby incorporated by reference intheir entirety.

BACKGROUND

The disclosure relates to an actuator for high precision positioningand/or manipulation of components, in particular of optical elements orother functional elements in projection exposure systems forsemiconductor lithography, and to a method for operating such anactuator. Here, the term “actuator” is to be understood as beingsynonymous with the terms “final controlling element” and “actuatingelement” that are likewise used.

There is a regular requirement for the abovenamed components to bepositioned and/or manipulated in the nanometer range in order to be ableto ensure the overall functionality of the higher level system. It isfrequently necessary in this context to monitor the position of thepositioned/manipulated components or the alignment thereof in space,with the aid of a high resolution and thus cost intensive and, as thecase may be, susceptible measuring and control electronics.

The accuracy of positioning and/or manipulation of conventional systemsis chiefly determined not by the actuator technology itself, but by theaccuracy of the position measurement. In other words, the actuators canhave smaller step widths than can be determined by the positionmeasurement.

However, the step width of the drive of conventional actuators canchange as a function of the load that acts on the movable part for theactuator. As a result of this, it can be impossible to calculate theoutput movement, and so the latter has to be monitored with a measuringsystem. In addition to this is the fact that slight deviation of thestep width can build up over longer travel paths of the actuator.

The problems described are explained below with reference to piezoactuators described in German Published Patent Application DE 100 225266 A1. DE 100 225 266 A1 describes an actuator for which the actuatormovable part (i.e., the moving part of the actuator, which acts on thecomponent that is to be manipulated and/or to be positioned) is drivenforward via one or more advancing elements (“feet”) that areperpendicular to the movable part. Here, the advancing elements move inthe direction of the movable part in a fashion perpendicular to theirown longitudinal direction.

Since such a foot also exhibits a certain compliance in the direction ofthe effective direction of the actuator, the step width that is producedby the foot is a function, on the one hand, of the force that the footitself can apply (advancing force), and on the other hand of the forceagainst which the foot starts to work, or of the force that exertstension or pression on the movable part of the actuator.

Consequently, a defined advancing force deflects the foot by a definedabsolute value, but owing to the compliance of the foot there issuperposed on this deflection a second deflection which results from theload on the movable part.

If, for example, a force acts on the movable part in the direction ofadvance, the step width becomes larger than the nominal step width, thatis to say the step width to which the actuator is designed. If, bycontrast, a force acts on the movable part against the effectivedirection, the step width becomes smaller than the nominal step width.In cases where the load on the movable part changes as the actuatortravels, the step width can also change therewith. Consequently, thestep width should be checked with an additional high precisiondisplacement sensor but, for reasons of design space and manipulation,this is not always desired or possible.

Another type of high-resolution step drives is the inertial drive. Withthese drives, an advancing element (e.g., a piezoceramic) pushes themovable part slowly in one direction via a friction contact. In thisprocess, the load on the movable part and the acceleration force on themovable part must be smaller than the transferable frictional force infriction contact. Subsequently, the advancing element is withdrawn witha jerk, the required acceleration force of the movable part being largerfor the quick backward movement than the frictional force that can betransferred in the friction contact. The movable part therefore remainsstationary, while the advancing element turns back in relation to themovable part. However, such drives have the disadvantage that they canexert only a slight force, since the force on the movable part togetherwith the acceleration force (inertial force) of the movable part is notpermitted to exceed the transferrable frictional force in the case ofthe forward movement.

Since, in addition, the movable part cannot be secured when theadvancing element is withdrawn with a jerk, the movable part can be“maladjusted” at this instant by an external force on the movable part.

SUMMARY

The disclosure features actuators which, in conjunction with a largeforce that can be exerted, permit a precise positioning and/ormanipulation on actuated components that is largely independent of load.

In general, in one aspect, the invention features actuators having aneffective direction that include a housing and a movable part that canbe moved in relation to the housing in the effective direction of theactuator, the actuator having an advancing unit that is at leasttemporarily connected to the movable part. The advancing unit exhibitsat least one deformation unit and at least one deformer for deformingthe deformation unit; the at least one deformer is suited to deform thedeformation unit with a vector component, in particular force component,perpendicular to the effective direction of the actuator in such a waythat the total length of the deformation unit changes in the effectivedirection as a result of the deformation.

The housing can include of least two housing parts that areinterconnected via the deformation unit and they can respectively haveat least one locking unit with the aid of which the movable part can belocked on the respective housing part.

The deformation unit can have at least one leaf spring, in particular itcan be designed as a pair of springs composed of two opposing leafsprings, at least two deformers being able to be arranged on the pair ofsprings in such a way that they can bend the springs toward one anotherfrom outside.

The movable part can have a first and a second partial movable part, thetwo partial movable parts being connected via the deformation unitdesigned as part of the movable part.

In this context, at least two locking units can be present which canrespectively lock one of the partial movable parts in relation to thehousing.

In order to inhibit the movement of the movable part in the effectivedirection of the actuator, the actuator can have damping elements.

In some embodiments, the deformation unit can have at least onepressurizable tube.

Alternatively, the deformation unit can have at least onetemperature-controllable bimetal, a magnetic spiral spring, a wirespring or else a combination of different spiral springs of differentcross section and/or different length.

The deformer can have a piezo element, in particular a piezo stack, anelectromagnetic coil, a hydraulic or pneumatic cylinder, or else apneumatic bellows. In addition, the deformer can be designed as acapacitor with capacitor plates whose electric field leads to adeformation of bending elements arranged between the capacitor plates.

In general, in another aspect, the invention features methods foroperating an actuator having a movable part that has a deformation unit,the methods including the following steps:

-   -   fixing the movable part by a first locking unit located upstream        of the deformation unit seen in the direction of movement of the        movable part,    -   releasing a second locking unit of the movable part that is        located downstream of the deformation unit seen in the direction        of movement of the movable part,    -   deforming the deformation unit by the deformer,    -   fixing the movable part by the second locking unit,    -   releasing the first locking unit, and    -   releasing the deformer from the deformation unit.

In this context, the individual method steps, in particular the two lastset forth, can deviate from the sequence given.

Further advantageous refinements and developments will be apparent fromthe claims and the embodiments described below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 a to 1 d show an embodiment of an actuator;

FIGS. 2 a to 2 d show another embodiment of an actuator in which avirtually unlimited travel path of the actuator is possible;

FIG. 3 shows an embodiment of an actuator in which damping elements areused;

FIGS. 4 a to 4 e show another embodiment of an actuator;

FIG. 5 shows a use of the actuator for high precision setting of paths;

FIGS. 6 to 19 c show implementations of deformers and deformationelements for applying various technical principles;

FIG. 20 is a schematic diagram illustrating a principle of actuatoroperation;

FIG. 21 shows an embodiment of a z-manipulator for a projection exposuresystem for semiconductor lithography using an actuator; and

FIG. 22 shows an embodiment of a projection exposure system forsemiconductor lithography.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

FIGS. 1 a to 1 d show an embodiment of an actuator 1. The actuator 1includes a housing 2 and a movable part 3 that is arranged therein andis held at least temporarily by the locking units 41 and 42. In thiscontext, the locking units 41 and 42 need not necessarily hold themovable part 3 through mechanical contact; it is also possible to applycontactless locking, for example by electric or magnetic forces. Alsoarranged in the housing 2 are deformers 5 which act on a deformationunit 6. In the example shown, the deformation unit 6 is designed suchthat it includes of two leaf springs 601 that interconnect the twopartial movable parts 31 and 32 of the movable part 3. The mode ofoperation of the inventive actuator 1 is explained below.

FIG. 1 a shows the first step in moving the movable part 3 in relationto the housing 2. In the method step shown in FIG. 1 a, the movable part3 is fixed on its partial movable part 31 by means of the locking units41; the right-hand partial movable part 32 can be moved freely; thelocking units 42 are open. The deformers 5, which act in a fashionperpendicular to the effective direction of the actuator 1, andtherefore perpendicular to the direction of movement of the movable part3, are also retracted into the housing 2.

In the second method step, illustrated in FIG. 1 b, the two deformers 5are extended and deform the leaf springs 601, which are arrangedopposite one another, toward one another so that a shortening of themovable part 3 in the direction of the arrow 700 occurs as a result ofthe deflection of the two leaf springs 601. In other words, theright-hand partial movable part 32 vibrates to the left, in thedirection of the left-hand partial movable part 31.

In the method step illustrated in FIG. 1 c, the right-hand partialmovable part 32 is locked by the associated locking units 42, while thedeformers 5 are again drawn into the housing 2 and release the leafsprings 601, although the locking units 41 by means of which theleft-hand partial movable part 31 is held are still closed in thisstate, and so the left-hand movable part 31 still cannot move, as aresult.

It is not until the fourth method step illustrated in FIG. 1 d that theleft-hand locking units 41 are opened and release the left-hand partialmovable part 31 which, as a result, executes a movement to the left inthe direction of the arrow 800. This concludes a complete cycle relatingto the movement of the movable part 3 in relation to the housing 2 ofthe actuator 1.

The steps illustrated in FIGS. 1 a to 1 d can in principle be repeatedfor as long as is allowed by the geometric conditions of the actuator 1,in particular the expansion of the leaf springs 601 in the effectivedirection of the actuator 1. It is also possible to operate the actuator1 illustrated in FIG. 1 in the direction both of tension and ofcompression, that is to say to connect either the right-hand partialmovable part 32 or the left-hand partial movable part 31 to an elementto be moved.

It may be seen from FIGS. 1 a to 1 d that the geometry of the actuator1, and in particular the fact that the leaf springs 601 are actuated ina fashion perpendicular to the effective direction of the actuator (thatis to say, perpendicular to the direction of the arrows 700 and 800) hasthe advantageous effect of producing, on the one hand, a high speedreduction ratio and, on the other hand, a high stiffness of the actuator1 in the effective direction.

The maximum force that can be applied by the actuator 1 illustrated inFIGS. 1 a to 1 d corresponds in this context to the Euler buckling loadof the leaf springs 601 for a compressive operation of the actuator 1;this restriction does not exist for a tensile operation of the actuator,but the maximum tensile force to be applied is restricted substantiallyby the force to be applied by deformers 5, and by the E modulus of theleaf springs 601.

The very high speed reduction ratio also enables the maintenance of aconstant defined step width irrespective of the load on the movable part3 by using a deformation restriction to precisely define the relativelylarge deformation of the leaf springs 601 perpendicular to the effectivedirection, with the result that the step width in the effectivedirection is also very precisely determined by the high speed reductionratio. By way of example, this deformation restriction can be realizedin the FIGS. 1 a to 1 d by virtue of the fact that the leaf springs 601are caused to sag until they abut one another.

FIGS. 2 a to 2 d show a variant of the invention in the case of whichthe travel path of the movable part 3 is virtually unrestricted. In thevariant illustrated in FIGS. 2 a to 2 d, the housing of the actuator 1is designed in two parts consisting of the two housing parts 21 and 22which are interconnected via the leaf springs 601. In this case,arranged in the first housing part 21 are the first locking units 41,while the second locking units 42 are arranged in the second housingpart 22. Likewise located in the first housing part 21 are the deformers5, which act on the leaf springs 601 in a fashion substantiallyanalogous to the variant illustrated in FIGS. 1 a to 1 d.

In the first method step illustrated in FIG. 2 a, the left-hand lockingunits 41 are closed and hold the movable part 3, while the right-handlocking units 42 are open so as to release the right-hand part of themovable part 3. The leaf springs 601 are relaxed, since the deformers 5are drawn in in the first housing part 21.

In the second method step illustrated in FIG. 2 b, the deformers 5 moveout from the first housing part 21 and deform the leaf springs 601 inthe way already known from FIG. 1, as a result of which the right-handhousing part 22 with the open locking units 42 moves in the direction ofthe first housing part 21 along the movable part 3. Subsequently(illustrated in FIG. 2 c), the right-hand locking units 42 are closed,as a result of which the movable part 3 and the left-hand locking units41 are opened. In the last method step, which is illustrated in FIG. 2b, the deformers 5 are withdrawn into the first housing part 21, as aresult of which the leaf springs 601 relax. Owing to the fact that inthe example shown in FIGS. 2 a to 2 d the deformation unit 6, that is tosay the leaf springs 601, are connected to the housing parts 21 and 22and not to the movable part 3, it becomes possible to displace themovable part in relation to the housing parts 21 and 22, virtually overan unrestricted distance.

Particularly in the embodiment illustrated in FIGS. 1 a to 1 d, it canhappen that when the locking units 41 are released, there is a suddenrelaxing of the leaf springs 601, and thus an unexpected impulse isexerted on the actuator 1. This problem can be mitigated or avoided, asillustrated in FIG. 3, by inhibiting the relaxation of the leaf springs601 and the movement, attended thereon, of the movable part 3 by the useof the dampers 7, thus permitting the above-described impulse to belargely avoided. The dampers 7 can be designed, by way of example, ashydraulic or else as electromagnetic dampers that are designed asimmersion coils.

FIGS. 4 a to 4 e shows an alternative possibility of preventing theimpulse upon the relaxation of the leaf springs 601. In essence, theillustration in FIGS. 4 a to 4 e correspond to the illustration in FIGS.1 a to 1 d; as shown in FIG. 4 d and FIG. 4 e, respectively, thedifference being that the leaf springs 601 are not relaxed until thedeformation unit 41 has released the left-hand movable part 31. Theleft-hand movable part 31 can then be controlled by the controlledwithdrawal of the deformers 5 in the housing 2.

The high speed reduction ratio that is implemented by the actuator 1also enables a fine adjustment of the movable part 3 or the actuator 1to be achieved by a doped actuation of the deformers 5, as illustratedin FIG. 5. A comparatively long path of the deformers 5 causes adecidedly short travel path of the movable part 3 owing to the geometricconditions of the invention. Thus, given knowledge of the geometricconditions and material constants, it suffices to measure the travelpath of the deformers 5, and then to infer the travel path of themovable part 3 that corresponds thereto. This variant of the inventionparticularly enables the use of a measuring system of low resolution tomonitor the travel path, since only the comparatively large travel pathof the deformers 5 need be measured. The conversion into the resulting,substantively smaller travel path of the movable part 3 is less affectedby errors because, firstly, the inventive actuator prevents a high speedreduction ratio and, secondly, the actuator is of decidedly stiff designin its effective direction such that the deformation of the movable part3 in the effective direction depends only to a very small extent on thecounterforce applied by the component to be actuated.

If the entire path that is covered by the movable part 3 is composed ofa plurality of individual steps, this path can be determined from thesum of the deformation movements by taking account of the preciselyknown speed reduction ratio between deformer 5 and movable part 3. It istherefore no longer necessary to make available a high precisionmeasuring system for the entire movable part travel path, as iscurrently required. With the actuator in accordance with the invention,it suffices to this end to make use for the deformer 5 of a measuringsystem that covers only the small travel range of the deformer 5 and,because of the high speed reduction ratio, has no need of resolution ashigh as the measuring systems previously used for this purpose.

Various possibilities for embodying the deformation units and deformerare sketched in FIGS. 6 to 19 c.

Thus, in FIGS. 6 to 9 the deformation units 6 are implemented as leafsprings 601 (only one leaf spring being illustrated in each case). Thedeformer is embodied in FIG. 6 as a piezo element 501, in FIG. 7 as anelectromagnetic coil 502 with iron core, in FIG. 8 as a hydrauliccylinder with associated hydraulic ram 503, and in FIG. 9 as a pneumaticbellows 504 between the two leaf springs 601. In FIG. 10, thedeformation unit is implemented as a thin-walled tube 610 to which acertain pressure can be applied from the tube interior. The tube 610 inthis case exhibits a double functionality as bellows and spiral spring.

FIGS. 11 a to 11 c illustrate the possibility of a thermal drive inwhich the deformation unit 6 is implemented as a pair of bimetal strips.The sagging of the bimetal strips 620 takes place in this case throughthe supply and removal of heat, as illustrated in subfigures 11 b and 11c. FIG. 11 a shows the arrangement in the neutral state. Likewise, thedeformation unit can be represented as a combination of two magneticcoils 505 with the magnetic spiral springs 630, as illustrated in FIG.12.

In addition, it is also possible to use as deformer a capacitor withcapacitor plates 506 whose electric field leads to a deformation of thebending elements 640 arranged between the capacitor plates 506.

FIGS. 14 to 19 c show further possibilities for forming deformationelement 6. The possibility, already presented, of a leaf spring 601 ispresented in FIG. 14, whereas a wire spring 650 is used in FIG. 15. Asillustrated in FIG. 16, it is also possible to consider a deformationelement 660 with any desired cross section. FIG. 17 shows a variant inthe case of which use is made as deformation element of a combination ofvarious spiral springs 670 of different cross section and differentlength, this enabling an adaptation of the actuator effect to therespectively prevailing requirements for the use of the inventiveactuator.

FIG. 18 shows a possibility where, in the effective direction of theactuator, the deformation unit has at least two sections with differentelastic properties. This is implemented by virtue of the fact that asolid intermediate piece 681 is arranged in the spiral spring 680. Adefined bearing surface for the deformers not illustrated in FIG. 18 isprovided by the solid intermediate piece 681. As a result, definedconditions for the action of force of the deformers on the deformationelement prevail over a restricted region even in the case of a sidewaysmovement of the movable part.

FIGS. 19 a to 19 c shows various possibilities for configuring asdeformation element 610 a thin-walled tube to which pressure can beapplied from inside.

The functional principle of the largely load-independent movable partstep width can be explained with the aid of FIG. 20:

The movable part with deformation unit is simulated by an equivalentmechanical model that consists of four rods which are interconnected bythree pivot joints, a torsion spring being arranged in parallel with themiddle pivot joint.

The inner rods respectively have the length a; the torsion spring hasthe torsion spring stiffness of k_(φ).

The rod outside on the right is secured by a locking unit, while the rodoutside on the left is guided linearly (for example by an open lockingunit).

The deformer has deflected the middle pivot joint via the path v, theinner rods thereby adopting the angle φ to the horizontal.

Acting on the rod outside on the left is the force F, which exerts onthe middle pivot joint the bending moment M_(bend) that tends to bendthe middle pivot joint. The bending moment M_(bend) results from theoffset of the path v and the force F

M _(bend) =F*v.

The path v is a function of the bending angle 2*φ of the middle pivotjoint via the length a of the inner rods, specifically

v=a*sin [(2*φ/2]=a*sin(φ).

A linearization can be adopted as an approximation for small paths v andangle φ for more specifically

v=a* _(T).

The bending moment M_(bend) can therefore be represented as a functionof half the bending angle φ of the middle pivot joint, specifically

M _(bend) =F*a*φ.

On the other hand, the torsion spring exerts on the middle pivot jointthe extending moment M_(extend) that tends to extend the pivot joint andthe overall movable part.

The extending moment M_(extend) is given by the bending angle 2*φ of themiddle pivot joint and the torsion spring stiffness k_(φ), specifically

M _(extend) =k _(φ)*2*φ=2*k _(φ)*φ.

The movable part is again extend completely when the bending momentM_(bend) is smaller than the extending moment M_(extend), specifically:

M _(bend) <M _(extend)

F*a*φ<2*k _(φ)*φ

F*a<2*k _(φ).

The inequality yields for the force F a bound that the force F may notexceed such that the movable part is again completely extended.

This bound is the critical force F_(crit), specifically

F<(2*k _(φ))/a=F _(crit).

Under the condition that the force F is smaller than the critical forceF_(crit) and remains so, the movable part again will extend completelysuch that the step width of the movable part, which results from theextending movement of the movable part, is independent of the force F.

The independence of the step width from the force F can be explained byvirtue of the fact that the extending moment M_(extend) about the zeroposition (extended position) of the movable part grows more stronglythan the bending moment M_(bend) when the force F is smaller than thecritical force F_(crit).

For a real leaf spring, the critical force F_(crit) corresponds to theEuler buckling load in the corresponding case of buckling load.

In addition that the deformation unit need not necessarily have elasticcomponents. It is likewise conceivable that the deformation of thedeformation unit is performed by a deformer that can exert both pressureand tension. This would then require the deformation itself notnecessarily to apply a restoring force.

Because of its high stiffness, its high positioning forces and itslargely load-independent step width, the actuator is suitable for areasof use in which, given a very high required positioning accuracy, ameasurement of the position of the object to be adjusted in order todrive the actuator can be implemented only with great difficulty, orthere is a need to position very large masses.

These requirements exist, for example, in the case of z-manipulators ina semiconductor lithography objective, which in order to correctaberrations position lenses very accurately in the z-direction beforeoperation begins, and finely set the lenses in the z-direction aboutthis position in real time during operation, in order to correctaberrations that are caused by fluctuation in the operating environment;an example is given in FIG. 21.

A z-manipulator can in this case be designed such that a lens 100 ismounted in an inner ring 101 that is, in turn, supported by threeactuators 1 in accordance with the invention, whose effective directionis oriented parallel to the z-direction.

The three actuators 1 are embedded in an outer ring 102 that, in itsouter region, forms the interface to the objective structure (notillustrated).

Owing to the high actuating stiffness, the actuators 1 can support theinner ring 101 together with the lens 100 directly in the z-direction,without the system composed of lens 100, inner ring 101 and actuators 1becoming susceptible to oscillation.

The sensor for the middle position 103 can be used to place the actuator1 approximately in the middle position again after a power failure.

In order to correct aberrations before operation, the actuators 1 canmove the lens 100 into the z-position in stepping mode, a sensor whichrecords exactly the z-position of the lens 100 not being required, sincethe step width is fairly accurately defined owing to its far reachingload independence. In order to reach the desired z-position, however,there is a need to count the number of steps executed.

The actuator 1 can be used in the fine adjustment mode in accordancewith FIG. 5 for the fluctuations about the middle z-position.

FIG. 22 illustrates a projection exposure system 310 for semiconductorlithography in which use is made of an actuator, such as those describedabove. The system serves to expose structures on a substrate that iscoated with photosensitive materials and generally consists mostly ofsilicon and is denoted as wafer 320, for the purpose of producingsemiconductor components such as, for example, computer chips.

The projection exposure system 310 includes an illumination system 330,a device 340 for holding and exactly positioning a mask, a so-calledreticle 350, provided with a structure from which the later structureson the wafer 320 are determined, a device 360 for holding, moving andexact positioning just this wafer 320, and an imaging device,specifically a projection objective 370, having a plurality of opticalelements 380 that are supported via mounts 390 in an objective housing400 of the projection objective 370.

The fundamental functional principle provides in this case that thestructures inserted into the reticle 350 are imaged onto the wafer 320;the imaging is executed with the demagnification.

After performance of exposure, the wafer 320 is moved further in thedirection of the arrow such that a multiplicity of individual fields areexposed on the same wafer 320, in each case having the structureprescribed by the reticle 350. Owing to the stepwise advancing movementof the wafer 320 in the projection exposure system 310, the latter isalso frequently designated as a stepper.

The illumination system 330 provides a projection beam 410, for examplelight or a similar electromagnetic radiation, for imaging the reticle350 on the wafer 320. A laser or the like can be used as the source forthis radiation. Radiation is shaped in the illumination system 330 viaoptical elements such that when impinging on the reticle 350 theprojection beam 410 has the desired properties with regard to diameter,polarization, shape of the wave front and the like.

The beams 410 generate an image of the reticle 350 that is transmittedon the wafer 320 by the projection objective 370 in an appropriatelydemagnified fashion, as has already been explained above. Projectionobjective 370 has a multiplicity of individual refractive, diffractiveand/or reflective optical elements 380 such as, for example, lenses,mirrors, prisms, closure plates and the like. In this case, one or moreof the optical elements can be arranged in a manipulator in the mannerof the manipulator illustrated in FIG. 21.

The z-direction is indicated in the present illustration in accordancewith FIG. 21.

Other embodiments are in the following claims.

1. An actuator, comprising: a housing; a movable part; and an advancingunit that is at least temporarily connected to the movable part, theadvancing unit comprising: a deformation unit; and a deformer configuredto deform the deformation unit with a vector component perpendicular toan effective direction of the actuator so that a total length of thedeformation unit changes in the effective direction of the actuator as aresult of the deformation, wherein the movable part is configured tomove in the effective direction of the actuator upon a removal of thevector component on the deformation unit and the deformation unit isdisposed along the effective direction of the actuator upon the removalof the vector component on the deformation unit.
 2. The actuator ofclaim 1, wherein the housing comprises two housing parts configured tobe interconnected via the deformation unit.
 3. The actuator of claim 2,wherein each housing part comprises a locking unit configured to lockthe moveable part to the housing part.
 4. The actuator of claim 3,wherein the deformation unit comprises a leaf spring.
 5. The actuator ofclaim 3, wherein the deformation unit comprises a pair of springscomprising two opposing leaf springs, and two deformers are arranged onthe pair of springs and configured to bend the leaf springs toward oneanother from outside.
 6. The actuator of claim 1, wherein the movablepart comprises first and second partial movable parts connected via thedeformation unit.
 7. The actuator of claim 6, further comprising twolocking units, wherein each locking unit is configured to lock acorresponding partial movable part relative to the housing.
 8. Theactuator of claim 1, further comprising damping elements configured toinhibit movement of the movable part in the effective direction of theactuator.
 9. The actuator of claim 1, wherein the deformation unitcomprises at least one element selected from the group consisting of apressurizable tube, a temperature-controllable bimetal, a magneticspiral spring, a wire spring, and a piezoelectric element.
 10. Theactuator of claim 1, wherein the deformation unit comprises acombination of different spiral springs of different cross sectionand/or different length.
 11. The actuator of claim 1, wherein thedeformation unit comprises two sections with different elasticproperties in the effective direction of the actuator.
 12. The actuatorof claim 1, wherein the deformer comprises at least one element selectedfrom the group consisting of an electromagnetic coil. a hydrauliccylinder, a pneumatic cylinder, and a pneumatic bellows.
 13. Theactuator of claim 1, wherein the deformer comprises a capacitorcomprising capacitor plates, which, during use, generate electric fieldthat lead to a deformation of bending elements arranged between thecapacitor plates.
 14. A system, comprising: an optical element; and anactuator as claimed in claim 1, wherein the actuator is configured tomove the optical element in a direction of an optical axis of thesystem, and the system is a semiconductor lithography projectionexposure system.
 15. The system of claim 14, wherein the optical elementis connected to further components of the projection exposure systemexclusively via the actuator and one or more additional actuators.
 16. Amethod of operating an actuator, the actuator comprising a housing, amovable part, a deformation unit and a deformer, the method comprising:fixing the movable part via a first locking unit, the first locking unitbeing located upstream of the deformation unit with respect to adirection of movement of the movable part; releasing a second lockingunit of the movable part, the second locking unit being locateddownstream of the deformation unit with respect to the direction ofmovement of the movable part; deforming the deformation unit via thedeformer; fixing the movable part via the second locking unit; releasingthe first locking unit; and releasing the deformer from the deformationunit so that the moveable part moves in an effective direction of theactuator, the deformation unit is disposed along an effective directionof the actuator upon releasing of the deformer from the deformationunit.
 17. An actuator, comprising: a housing comprising two parts; amovable part; a deformation unit; and a deformer configured to deformthe deformation unit with a vector component perpendicular to aneffective direction of the actuator so that a total length of thedeformation unit changes in the effective direction of the actuator as aresult of the deformation, wherein the deformation unit is connected tothe two parts of the housing and not to the movable part so that themovable part can move in relation to the two parts of the housing overan unrestricted distance.
 18. The actuator of claim 17, wherein each ofthe two parts of the housing comprises a locking unit configured to lockthe moveable part to the respective part of the housing.
 19. Theactuator of claim 17, wherein the deformation unit comprises a leafspring.
 20. The actuator of claim 17, wherein the deformation unitcomprises a pair of springs comprising two opposing leaf springs,and-two deformers are arranged on the pair of springs and configured tobend the leaf springs toward one another from outside.
 21. A system,comprising: an optical element; and an actuator as claimed in claim 17,wherein the actuator is configured to move the optical element in adirection of an optical axis of the system, and the system is asemiconductor lithography projection exposure system.
 22. The system ofclaim 21, wherein the optical element is connected to further componentsof the projection exposure system exclusively via the actuator and oneor more additional actuators.
 23. A method of operating an actuator, theactuator comprising a housing, a movable part, a deformation unit and adeformer, the housing comprising two parts connected via the deformationunit, the method comprising: fixing the movable part via a first lockingunit, the first locking unit being located upstream of the deformationunit with respect to a direction of movement of the movable part;releasing a second locking unit of the movable part, the second lockingunit being located downstream of the deformation unit with respect tothe direction of movement of the movable part; deforming the deformationunit via a deformer; fixing the movable part via the second lockingunit; releasing the first locking unit; and releasing the deformer fromthe deformation unit so that the moveable part moves in an effectivedirection of the actuator over an unrestricted distance.